Whitefly: potato and cabbage pest in Indonesia and Western Australia

Page last updated: Friday, 3 July 2020 - 12:25pm

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Whitefly is a relatively minor pest of potato and cabbage crops in both Indonesia and Western Australia.

The Department of Agriculture and Food, Western Australia has worked with the Indonesian potato industry to increase the productivity of Indonesian crops planted with WA seed potatoes.

Improved productivity requires accurate identification of pests in potatoes and also as in the cabbage rotation crop.

As well as helping Indonesian farmers this information will assist Western Australian seed potato exporters understand the challenges their Indonesian customers face.

Identification

The Indonesian name for whitefly is "kutu putih" and it is in the insect family Aleyrodidae.

Whiteflies reduce potato and cabbage plant vigour by sucking sap from leaves. There are several species, but all adults are small at about 1.5mm long with white wings.

Whitefly adults and eggs on the underside of young leaves – white eggs are newly laid and darker eggs are close to hatching
Whitefly adults and eggs on the underside of young leaves

Adults lay eggs on the underside of young leaves. The eggs are pale when first laid and turn black just before hatching into nymphs.

Whitefly nymphs settle and feed on the underside of leaves
Whitefly nymph
Young whitefly nymphs and an aphid (the larger insect). Whitefly and wingless aphids are similar but whitefly do not have cornicles on each side of the end of the aphid's body. Also aphids move around but whitefly feed in the one position
Young whitefly nymphs and an aphid (the larger insect)

Whitefly immature stages are called nymphs which occur on the undersides of leaves. They are grey to white, circular and soft-bodied, similar to aphid nymphs. But unlike aphids, whitefly nymphs lack cornicles on the abdomen and do not move once they start feeding.

Sooty mould is a fungus that develops on honeydew excretions on leaves from feeding by nymphs and adults of whiteflies
Sooty mould caused by whitefly feeding

Symptoms of whitefly damage include wilting leaves and the presence of black sooty mould. These symptoms are rarely seen because only large numbers of whitefly will cause such effects. The sooty mould is a fungus that grows on the sugary honeydew that nymphs and adult whitefly excrete when they are feeding.

Cocoons of whitefly - cream ones are healthy, unparasitised; yellow ones are parasitised. Cocoons from which whitefly adults have emerged are grey, empty with a split and cacoons from which a wasp emerged have a circular hole chewed in them
Cocoons of whitefly - healthy and parasitised

When mature, whitefly nymphs form into white oval cocoons on the underside of leaves. Cocoons are cream when not parasitised, yellow when parasitised.

Cocoons from which whitefly adults emerge are grey shells with a split line, and cocoons from which wasp parasites have emerged have a circular hole cut in them.

A video on whitefly stages is available.

Management

Whitefly may be present on weeds so keep the area around crops free of weeds.

Check crops for whitefly during weekly pest monitoring.

Whitefly will cause damage only when present in high numbers.

Several species of whitefly can be pests in potato and cabbage crops. Some of these have a reputation for developing resistance to insecticides so careful consideration is required as to whether infestations require insecticide use and whether natural enemies may control an infestation.

If insecticides are used, delay or avoid insecticide resistance by alternating insecticides with different modes of action.

Natural enemies of whitefly include wasp parasitoids, and predators such as lacewing larvae, ladybird beetles, hover flies, mites and spiders.

This wasp is a natural enemy of whiteflies
This wasp is a natural enemy of whiteflies
Green lacewing adults are about 15mm long, green and have reflective green/brown eyes. They feed on nectar and pollen. Their larvae are predators of whitefly
Green lacewing adult
Green lacewing larvae feed on whitefly as well as other small insects or eggs. They place dried chewed prey on their back
Green lacewing larva
Predatory ladybird adult beetle which is orange with black spots and its egg mass of yellow eggs laid upright. The adult beetle and its larvae fed on whitefly nymphs
Ladybird adult and yellow egg mass next to whitefly nymphs

If whitefly numbers are high enough to cause crop wilting, insecticides should be applied. A range of contact, systemic and growth regulator insecticides will control whitefly and more than one application may be required to control heavy infestations.

Acknowledgment

Funding for this work to support Indonesian potato farmers and WA seed potato exports was provided by ACIAR (the Australian Centre for International Agricultural Research) and the Department of Agriculture and Food, Western Australia.

Contact information

Stewart Learmonth
+61 (0)8 9777 0167

Whitefly: potato and cabbage pest in Indonesia and Western Australia

Author

Stewart Learmonth